strace

strace  for troubleshoot , to know the system call, know the opened file 

system call, interface between an application and linux kernel      execute() clone()

 

strace-o write output to file

strace -e trace a particular system call  e.g strace -e trace-open ls 

 

strace -f  follow child  process

strace -p process id 

strace -count time, calls, and errors for each syscall and report summary